CHAPTER XVI 



HOST-PARASITE RELATIONS AMONG 

 TRICHOMONADS 



By 



John F. Kessel 

 School of Medicine, University of Southern California 



INTRODUCTION 



Three types of Trichomonas, one with three anterior flagella, 

 one with four anterior flagella, and one with five anterior flagella, 

 have been reported from man. Of these, the type with four an- 

 terior flagella, or Trichomonas hominis, is the most common. 



Many of the lower mammals have also been shown to harbor 

 trichomonads, and these may be roughly divided into two main 

 types morphologically. One is massive in structure with a heavy 

 axostyle, pronounced parabasal body, prominent undulating mem- 

 brane, and forms cysts, e.g., Trichomonas muris of the white rat, 

 and Trichomonas cavice of the guinea-pig. This variety may, for 

 convenience, be designated as the Trichomonas muris type. It has 

 never been reported from man and has not been transferred to 

 kittens, though one of the smaller trichomonads of the rat, either 

 T. parva or T. minuta has (see Kessel, I928r). It accordingly 

 appears that this type in addition to possessing a characteristic 

 morphology may possess certain definite cultural and host restric- 

 tions. One would therefore expect transmission experiments with 

 this first type to be most successful between those hosts that harbor 

 morphologically similar forms, i.e., between the guinea-pig and 

 the rat. 



The other type exhibits a much more delicate gross appearance, 

 the axostyle is much lighter in structure, the parabasal body is 

 difficult to detect, and the undulating membrane is much less 

 prominent. This general type is exhibited in the three trichomon- 



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